Polyoma nucleoprotein complexes (polyoma chromosomes) were induced to replicate by incubation in cytoplasm prepared from eggs of the frog, Xenopus laevis. 3H dTTP was incorporated into polyoma replicative intermediates, and the formation early or late "Cairns" structure was observed by electron microscopy. The goals of this project are (1) to characterize the input polyoma nucleoprotein complexes by biochemical and electron microscopic techniques, (2) to purify milligram quantities of the relevant DNA replication enzymes found in the Xenopus laevis eggs, (3) to reconstitute the purified components to give in vitro chromosome replication, (4) to identify the role of each purified component in polyoma DNA replication, (5) to evaluate the role of histones and other chromatin-associated proteins in the replication process, (6) to evaluate the role of polyoma T antigen (ts A protein) in the replication process, and (7) to examine the role of host nuclear components on polyoma chromosome replication. We will use the data to develop a model relating the enzymology of DNA synthesis using purified DNA templates in vitro with the replication of eukaryotic nucleoprotein complexes observed in vivo.